The intent behind the Dublin and Monaghan UVF bombs that killed 34 people, including an unborn baby, was to foment a civil war, one of the gang members has claimed.
UVF man John Weir told RTE documentary Collusion that the terror gang was confident when civil war erupted they could then "crush the other side".
Weir, who served as an RUC officer, was not a member of the terror group at the time of the bombings.
Three car bombs in Dublin and a fourth in Monaghan exploded without warning, injuring almost 300 people and killing 34, the greatest loss of life on a single day during the Troubles.
No one was ever charged in connection with the atrocities of May 17, 1974.
There have been continuing allegations of collusion between the UVF militants responsible and elements of the British security and intelligence services.
The UVF only admitted responsibility for the attacks in 1993, but did not give any motive for them.
However, in a first television interview Weir, who was part of the notorious Glenanne gang that carried out sectarian attacks in the mid-1970s, revealed the UVF wanted a civil war.
The documentary also claims to reveal how the British Government denied that collusion existed.
According to the programme, Taoisigh Jack Lynch and Liam Cosgrave were met with flat denials when they raised collusion with their British counterparts.
The programme claims there is strong evidence to prove that the British were well aware it existed.
The past is not just about collusion. Not just about the Special Branch, the military, MI5 and their agents. Their stories are part of what has come to be called a "dark side" or a "dirty war". They are a poison that seeps from the past and, at times, floods the present.
More secrets from the dirty war that was Northern Ireland's Troubles are set to emerge in an RTE documentary next Monday and they could prove to be the most explosive yet. The programme claims that knowledge of collusion between the security forces and loyalist paramilitaries went right to the top of the British Government, with former Prime Minister Margaret Thatcher turning a blind eye to it.